In my U.S. Pat. No. 4,259,538, entitled, "Vacuum Furnace Arrangement Having An Improved Heating Element Mounting Means", I described the problems that arise in connection with operating a vacuum furnace structure which has the insulating material and the heating element, or heating elements, mounted in the heating chamber of the vacuum furnace by a plurality of suitably attached molybdenum rods. The molybdenum rods are conductors of electricity and accordingly must be electrically insulated from the heating element which provides heat (by passing electrical current therethrough) in accordance with its electrical resistance characteristics (I.sup.2 R). It was determined by me at the time of the invention, described and claimed in the above mentioned patent, that electrical insulator devices should be employed to separate the molybdenum mounting rods from the heating element. It was also determined at that time that some of the work piece material evaporates and condenses on the insulator devices to provide a material buildup between the molybdenum rod and the heating element thereby providing a "short circuit". The above mentioned patent teaches the use of molybdenum shields to partially block the space between the molybdenum rod and the electrical insulator device so that no buildup of material can occur therebetween. At the same time said molybdenum shields intercept vaporized work piece material before it condenses on the outer surfaces of the electrical insulator devices. The foregoing described shields have worked out satisfactorily except in certain situations where the temperatures have been sufficiently high and the cycling time sufficiently long, so that the molybdenum shield material, per se, has vaporized and simultaneously the minute amounts of water vapor, (in what would otherwise be a true vacuum), have broken down into hydrogen and oxygen. It was principally the recognition of this last mentioned phenomenon that led to the conception of the present invention. After careful analysis it was determined that under the circumstances of high temperatures and relatively long cycling times, a certain amount of molybdenum from the molybdenum shields was in vapor form and the presence of the oxygen, from the water vapor, acted to oxydize such vaporized molybdenum. It was further determined that the electrical insulator devices have an affinity for molybdenum trioxide (MO.sub.3). It was also discovered that while the molybdenum shields intercepted the vaporized work piece material such shields, per se, provided a buildup of MO.sub.3. On subsequent cycles the MO.sub.3 is reduced to leave molybdenum on the insulator surfaces and such a molybdenum buildup conducts electricity. The present invention serves to overcome that problem.